Warewash processes may involve at least two steps, a main wash and a rinse step. In the main wash, the substrates are cleaned by pumping main wash solution over the substrates via nozzles. This main wash solution is obtained by dissolving main wash detergent, which can contain components such as alkalinity agents, builders, bleaches, enzymes, surfactants for defoaming or cleaning, polymers, corrosion inhibitors etc. In the rinse step after the main wash, warm or hot water containing rinse aid solution is flown over the substrates, which can be followed by a hot air stream to further improve the drying process. The rinse aid typically consists of non-ionics present in an amount of 10 to 30% in water; often in combination with hydrotropes and sometimes other additives such as polymers, silicones, acids, etc.
International patent application WO 2008/147940 (not pre-published) discloses the inclusion of a polysaccharide in the main wash detergent as a built-in rinse aid. This patent application discloses that polysaccharides adsorbing on the ware in the main wash process result in a sheeting action and good drying properties in all water qualities. The best drying properties are obtained with a cationic guar (e.g. Jaguar C1000), which provides very good drying on glass and metal substrates and reasonable drying on plastic materials.
JP 2007-169473 discloses a cleanser composition for dish washers comprising a cationized water-soluble polysaccharide and a nonionic surfactant, the weight ratio of the polysaccharide to nonionic surfactant being 3/1 to 1/10. In the Examples, the performance of three cationic celluloses and one cationic starch, together with nonionic surfactants, is reported. The weight ratios of nonionic surfactant to cationic starch varies in these examples from about 3/1 to 8/1. Firstly, cationic celluloses have the disadvantage that the high foam level created by these celluloses will limit their use for mechanical ware washing, because foam will reduce mechanical action in the washing process and so reduce cleaning of the substrates. Secondly, the high weight ratios of nonionic surfactant to cationic starch and the reletively high level of nonionic surfactant applied together with cationic starch were found to be disadvantageous for ware washing by having a negative effect with regard to cleaning and drying, providing chemical instability together with chlorine, providing substantial foaming, providing physical instability in liquid compositions, providing inferior flowing properties of solid compositions and hindering tablet or briquet production.
Surprisingly, it was now found that cationic starches overcome some of the limitations of cationic guars and cationic celluloses. Cationic starches can even further improve drying performance as compared to cationic guar, leading to very good drying on any type of substrate, including plastic materials. Cationic starches further have an improved performance when only low levels of nonionic surfactant are provided in the washing solution, in particular when no nonionic surfactant at all is provided. Furthermore, cationic starches have good non-foaming properties, much better than those of cationic celluloses. Even in combination with various soils only low levels of foam are formed in the mechanical warewashing process containing cationic starch, while a similar process with cationic guar will be much more sensitive for foam formation. Furthermore, cationic starches, as Hi-Cat CWS 42, are approved for indirect food contact and are easily available. Finally, cationic starches, such as Hi-Cat CWS 42, can be easily incorporated in solid granular detergents without the risk of phase separation. Segregation of particles is prevented due to the relatively large particle size of this cationic starch.